Requirements

PHP

PHP 8.4 or newer.

Runtime dependencies

None. The package requires nothing but PHP itself.

The engine is pure: it reads a document, answers questions about it, and writes it back out. It executes no jobs, opens no connections, and persists no state, so there is nothing for a dependency to do. Keeping the requirement empty means the package can sit in any application without pulling a tree of its own behind it.

Optional

Package	What it adds
azuyalabs/yasumi	Public holidays resolved automatically, without writing a resolver of your own

The engine asks a resolver for the dates behind a name such as holidays. You can supply one yourself — see Supplying dates at runtime — or install yasumi and let the package resolve them. It is a Composer suggest, so nothing is installed until you ask for it.

Timezone data

Interpretation follows the timezone declared in the document, resolved against the tz database available to your PHP installation. Whether a zone name exists, and where its transitions fall, is therefore a property of the host rather than of the document. Keeping the tz data current is part of keeping the host current.